2018-06-15 Rec v21r7

This version uses Lbcom v20r7p1, LHCb v42r9, Gaudi v28r2p1 and LCG_88 with ROOT 6.08.06.

This version is released on `2017-patches` branch.

Built relative to Rec v21r6p2, with the following changes:

Enhancements

• Add PartProp dependency to follow LHCb!1308, !1052 (@cattanem)

Bug fixes

• Protect from division by zero in PrCounter2, !1091 (@sstahl)
  Cherry picked from !1088 in master

• Correctly set the RichPID container version, !1007 (@jonrob)
  Cherry-picked from !1000 in 2018-patches
  Fixes the bug discussed in LHCb!1245

Code modernisations and cleanups

• adapt to change in CaloHypo::setPosition, !1025 (@deschamp)